Control of Rush Skeletonweed (Chondrilla juncea) with Herbicides

A range of herbicide treatments was evaluated for long-term control of rush skeletonweed, a perennial weed of crops and pastures in North and South America, the Mediterranean region, central Europe, and Australia. Clopyralid (75 to 300 g ai/ha) and clopyralid mixtures with 2,4-D, MCPA, or dicamba were effective, resulting in survival rates of 0 to 4% for the most successful treatments applied for three consecutive seasons. Metsulfuron (9 g ai/ha) and 2,4-D (850 g ai/ha) significantly reduced survival when applied at high rates for three years. Barley yield in the season following control was increased by up to 195 to 199% of yield from untreated plots. Evidence was found for differences in herbicide susceptibility between narrowleaf and broadleaf forms of rush skeletonweed. Nomenclature: Clopyralid, 3,6-dichloro-2-pyridinecarboxylic acid; dicamba, 3,6-dichloro-2-methoxybenzoic acid; MCPA, (4-chloro-2-methylphenoxy)acetic acid; metsulfuron, 2-[[[[(4-methoxy-6-methyl1 ,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]benzoic acid; 2,4-D, (2,4-dichlorophenoxy)acetic acid; rush skeletonweed, Chondrilla juncea L. #3 CHOJU; barley, Hordeum vulgare L. Additional index words: Perennial weed, long-term control, yield increase, picloram. CHOJU.